The rate of deposition and removal of a radioactive milk soil from several surfaces have been studied. The nature of the surface exhibited a small but measurable effect on the rate of deposition of a radioactive milk soil on the surfaces tested. However, the surfaces showed no significant effect on the rate of soil removal. The build-up that took place on all surfaces due to repeated soilings without washing was not a simple additive accumulation of residue but appeared to be a selective deposit of a residue slowly laid down over a period of time and difficult to remove. As the accumulated residue increased, a point was reached beyond which there was no significant difference among surfaces in the rate of soil build-up. Subsequent washing removed only part of the soil and even repeated washings had little effect unless special heavy duty cleaning was applied.
No significant difference was found in the relative cleanability of Nos. 2B, 3, 4, and 7 stainless steel finishes as measured by bacteriological tests. Therefore, it can be concluded that from a bacteriological cleanability stand-point, based on the conditions of this study, the selection of a stainless steel finish from among those used in these studies for a farm bulk tank or any comparable piece of equipment should be based on factors other than bacteriological cleanability.